1. Field of the Invention
This invention relates to agricultural implements and, more particularly, to an apparatus for sensing the hardness of subjacent soil and controlling downward pressure on agricultural implements in relation to the soil hardness to assure uniform depth of treatment with the implements.
2. Background Art
A primary objective of the agricultural industry is to optimize field productivity by producing a uniform crop yield throughout an entire field. Yield plotting and other types of field monitoring have allowed farmers to control the application of fertilizer, pesticides, etc. to maximize crop output. Even with the sophisticated monitoring that is presently carried out, the inconsistency in soil hardness has been a prevailing problem that causes a significant variation in crop quality and volume throughout a field.
Several factors contribute to the hardness of soil. For example, the amount and timing of rainfall are major factors in determining soil hardness. Changing of the nature of areas surrounding fields may alter drainage characteristics in the fields. Wind may relocate soil to change the field contour and the soil composition. All of these factors, and others, change the soil hardness from one year to the next and sometimes from one location to the next in the same field. Since most of these factors are unpredictable, it is impossible to prepare in advance for soil conditions that will exist during planting season. Whereas the above monitoring techniques have enabled farmers to compensate for some variables and thereby greatly increase production for a given field, no suitable structure is currently available to effectively compensate for variations in soil hardness.
Typically, agricultural implements are generically designed for a standard soil type. That is, the implements are weighted so that soil penetrating tools, such as fertilizer applicators, soil openers, etc. penetrate the soil a predetermined depth under the overall weight of the implement. A typical implement may weigh on the order of 300 pounds. In exceptionally soft soil, the tools on the implement penetrate a significantly greater amount than is desired, so that the wheels create unwanted trenches, while in particularly hard soil an inadequate amount of penetration of the tools may result. This results in inconsistent depth of seed and fertilizer placement, which may in turn result in significantly different crop quality and yield for different parts of a field.
It is known to produce a downward biasing force on implements to increase the penetrating depth of the tools thereon in harder soils and also to avoid uncontrolled bouncing of the implements, particularly when they are drawn over such harder soils. In one known system, a spring mechanism acts between a rigid carrying frame and a linkage, or other mounting part for the implement, to exert a downward force. Without the ability to vary this added downward force, the farmer solves the penetration problem only for the harder soils and aggravates the problem by causing excessive penetration in the softer soils.
In an attempt to overcome this problem, mechanisms have been devised to adjust spring position as to allow variation in the magnitude of the downward spring force. One such prior art system uses one fixed position spring and one variable position spring in association with each implement. This generally requires that the user manually set, one by one, the adjustable springs associated with each of the implements. Since a multitude of adjustments may actually be required over a given field, adjustment is a time consuming and very inconvenient exercise. As a result, the user may make a compromise adjustment that is adequate for the entire field yet which fails to optimize yield for the harder and softer soils.
To overcome the deficiencies in the last described system, it is known to use a pneumatic system to vary downward pressure on tools. This system requires a separate compressor to be operated by the towing vehicle. If multiple implements are to be simultaneously controlled, an impractically large holding tank would be required. It is inconvenient to have to provide a self-contained air compressing system, which takes up valuable space on the towing vehicle. Further, pneumatic cylinders are normally quite large and may interfere with an operator's access to the implements as may be required to effect adjustments or repairs thereto. In spite of this problem, one agricultural equipment manufacturer uses an air cylinder, such as used as a shock absorber on an automobile, to prevent implement bouncing and exert a downward force on the implements.
Another problem with this system is that the manner of detection of the soil hardness is deficient. The operator is required to "guess" at the hardness of the soil in front of the towing vehicle, based upon the physical appearance thereof and make a relatively crude adjustment in anticipation of encountering this soil. Alternatively, the operator can visually monitor the amount of penetration of the tools behind the towing vehicle and then make an adjustment. However, at this point, a significant amount of the soil will have been treated before the appropriate adjustment can be made. This also requires the constant attention of the operator whose attention is normally required for other important tasks.
While the above described deficiencies in the prior art have been recognized for a long time, for want of any better solution, these systems have generally been practiced and their shortcomings contended with.